judgecorp writes: "Britain is considering switching off air traffic control radar systems and using "passive radar" instead. A two year feasibility study will consider using a network of ground stations which monitor broadcast TV signals and measure echoes from aircraft to determine their location and velocity. The system is not a new idea — early radar experiments used BBC shortwave transmitters as a signal source before antenna technology produced a transceiver suitable for radar — but could now be better than conventional radar thanks to new antenna designs and signal processing techniques. It will also save money and energy by eliminating transmitters — and release spectrum for 5G services."